Functional studies of two cloned non-allelic human methionine initiator tRNA genes were continued. One of the cloned genes, containing a variant sequence, was shown to direct the synthesis of a mature variant initiator tRNA met species following injection of either the cloned gene of primary transcript into the intact laevis germinal vesicle. Unlike the normal initiator tRNA nmet species which was efficiently transported from the oocyte nucleus, the newly synthesized variant initiator tRNA met accumulated within the nucleus, limited from escape by the nuclear membrane. Combined with our previous in vitro studies, the data demonstrate that while processing and transport of tRNA species are functionally linked, they nonetheless can be uncoupled within the intact cell; and they provide the strongest argument to date that the processing endonuclease may be a component in the tRNA transport mechanism.